The Free Electron Laser
We have investigated the possibility of a new type of laser by computer simulation using a 1–2/2 dimensional fully relativistic electromagnetic particle code. By passing a relativistic electron beam over a rippled static magnetic field, high frequency electromagnetic radiation is generated. If the ripple wavelength is λo, the lasing wavelength is roughly λo /2γ2. Thus such a laser is continuously tunable by varying γ. We also find that as much as 35% of the beam energy can be converted into radiation, of which as much as nearly 90% can be in the most rapidly growing mode. A theory of the coupling between the negative energy plasma wave and electromagnetic radiation by means of the rippled magnetic field is presented. We have obtained good agreements between the simulation and the theory. The saturation mechanism is found to be the trapping of the beam by the unstable plasma wave. We are also able to estimate theoretically the amount of energy that can be converted into radiation from the electron beam.
KeywordsElectromagnetic Wave Electromagnetic Radiation Plasma Wave Free Electron Laser Relativistic Electron Beam
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- 1.Science 187, No. 4181, March 21, 1975, Research News.Google Scholar